It has long been known that cardiac dysfunction induces a series of events that ultimately contribute to congestive heart failure (“CHF”). One such event is a reduction in renal blood flow due to reduced cardiac output. This reduced flow can in turn result in the retention of excess fluid in the patient's body, leading for example, to pulmonary and cardiac edema.
Chapter 62 of Heart Disease: A Textbook of Cardiovascular Medicine, (E. Braunwald, ed., 5th ed. 1996), published by Saunders, Philadelphia, Pa., reports that for patients with CHF, the fall in effective renal blood flow is proportional to the reduction in cardiac output. Renal blood flow in normal patients in an age range of 20-80 years averages 600 to 660 ml/min/m2, corresponding to about 14 to 20 percent of simultaneously measured cardiac output. Within a wide spectrum of CHF severity, renal blood flow is depressed to an average range of 250 to 450 ml/min/m2.
Previously known methods of treating congestive heart failure and deteriorating renal function in patients having CHF principally involve administering drugs, including diuretics that enhance renal function, such as furosemide and thiazide, vasopressors intended to enhance renal blood flow, such as Dopamine, and vasodilators that reduce vasoconstriction of the renal vessels. Many of these drugs, when administered in systemic doses, have undesirable side-effects.
In addition, for patients with severe CHF (e.g., those awaiting heart transplant), mechanical methods, such as hemodialysis or left ventricular assist devices, may be implemented. Mechanical treatments, such as hemodialysis, however, generally have not been used for long-term management of CHF.
Advanced heart failure (“HF”) requires the combination of potent diuretics and severe restriction of salt intake. Poor patient compliance is a major cause of refractoriness to treatment. On the other hand, as renal urine output decreases with reduced renal perfusion, in the event of dehydration, the required diuretic dosages increase.
In view of the foregoing, it would be desirable to provide methods and apparatus for treating and managing CHF without administering high doses of drugs or dehydrating the patient.
It further would be desirable to provide methods and apparatus for treating and managing CHF by improving blood flow to the kidneys, thereby enhancing renal function.
It also would be desirable to provide methods and apparatus for treating and managing CHF that permit the administration of low doses of drugs, in a localized manner, to improve renal function.
It still further would be desirable to provide methods and apparatus for treating and managing CHF using apparatus that may be percutaneously and transluminally implanted in the patient.